Instagram photos were originally restricted to a 1:1 aspect ratio, meaning they had to be square. The limitation was one of the app’s defining early visual traits and helped give Instagram its instantly recognizable look.
The square format was partly practical and partly stylistic. Early Instagram was designed around the iPhone, and the original service used 640-pixel-wide images. A fixed square frame simplified the feed, thumbnails, editing tools, and profile grids, while echoing the look of instant-camera and medium-format square photography.
The restriction was relaxed in August 2015, when Instagram added support for portrait and landscape—or widescreen—photos. Users no longer had to crop every image into a square before posting. That change made the service more compatible with photographs taken on phones and cameras using common 4:3, 3:2, or widescreen proportions.
The ratio is often confused with a camera’s native format. A phone may capture a 4:3 image, but early Instagram would crop it to 1:1. The numbers describe width-to-height proportions, so 1:1 produces equal sides rather than a rectangular frame.